Having defined the transcriptional program regulating myogenesis during embryogenesis for posterior blastomeres in C.elegans, we have turned our attention of understanding the regulation of muscle born from more anterior blastomeres. This is a much more complex process as cells undergo a number of divisions, migrations, interactions, and intermediary specification before executing terminal differentiation. Using a combination of lineage-specific reporter genes and antibodies, we have perturbed the system by mutation or RNAi-mediated gene knockdown to study the process. We have combined this with transcriptional profiling in embryos manipulated to produce mostly anterior muscle tissue. This combination of approaches has allowed us to identify which transcription factors play a role in the progressive process of myogenic specification from anterior blastomere lineages. Our results reveal a remarkably complex set of factors are required in different combinations to specify muscle, ultimately leading to the activation of the core myogenic transcriptional regulators. We have begun to examine the extrinsic and intrinsic signals regulating polarity in the animal using the regulation of a gene that is expressed preferentially in the ventral bodywall muscle. We are trying to determine the cis-acting elements in the promoter of this gene and how they function relative to extracellular signals.